


Dangerous Impulse

by The_Winter_Writer



Series: Bingo Challenge [12]
Category: Marvel Cinematic Universe, The Avengers (Marvel) - All Media Types
Genre: Alternate Universe, Barebacking, Bottom Tony, Creature Loki, Loki (Marvel) Does What He Wants, M/M, Magic-Users, Merman Loki, Mythical Beings & Creatures, Ocean Sex, POV Tony Stark, Possessive Loki (Marvel), Rough Sex, Size Difference, Size Kink, Size Queen Tony Stark, Tony Stark Does What He Wants, Top Loki
Language: English
Status: Completed
Published: 2018-01-07
Updated: 2018-01-07
Packaged: 2019-03-01 19:28:05
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,654
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13301649
Author URL: https://archiveofourown.org/users/The_Winter_Writer/pseuds/The_Winter_Writer
Summary: Tony had always had a fascination with danger. It helped him to push harder and faster; to try things others thought impossible. It shouldn't come as a surprise that he followed that same impulse when it came to a wickedly tempting merman.





	Dangerous Impulse

**Author's Note:**

> It's been awhile! At least it feels that way. I've been a bit stuck on these last two squares needed to completely my W-shape bingo. I tried this one six different ways and decided to go the pure smut route mostly because I somehow keep writing things that are begging for more. I also have been drowning myself in Star Wars and it's made focusing on purely Marvel a bit harder (I've been into Star Wars since I was around six and get overly excited about anything new).
> 
> My twelfth bingo square in my quest for a W-shaped bingo is G4: Merman/Human AU. This is my first purely FrostIron and I'm still not happy with it but I'm satisfied with where I left it.

It wasn’t the smartest thing he’d done. Tony _knew_ he should be careful, he should be wary, but he’d never been very good at doing what he should and sometimes recklessness ended in nothing but pleasure. It didn’t help that he was several years out of MIT, staring down the barrel of true adulthood and responsibility in the form of taking over Stark Industries.

The impulse to do something stupid, something inadvisable, was too much to resist at times.

Loki was probably the biggest and most dangerous impulse. The merman had actually offhandedly mentioned being a sea witch but a little thing like that wasn’t going to deter Tony from sating his curiosity and then his interest. It didn’t help that the temptation was too great, the first taste of reward too good and the need to keep going difficult to ignore.

This wasn’t the most comfortable place, the rocks both warm and wet, but these particular rocks sloped perfectly into the water and were angled right for him to be draped over. Unfortunately there was nothing he could hold onto. Tony could only lie there, panting and whining, as Loki started to push into him while the sun started to dip lower.

A human wasn’t built to handle the impossible size of a merman, unnaturally long and thick to aid breeding with their own kind, but the impossible had never stopped Tony and Loki was _very_ persuasive.

Tony also happened to have a size kink the size of Texas that only a monstrously large toy could have helped and Loki’s kind was naturally gigantic in all the best, if a bit painful, ways. Denying himself, after realizing where the unusual relationship was going, never even crossed Tony’s mind.

A high, reedy kind of sound ripped out of him as Loki kept pushing into him and Tony could feel how Loki’s now unsheathed cock thickened more and more the closer it got to the base as it edged in. The crash of the waves failed to drown out the wrecked sounds Loki was effortlessly pulling from him and distantly Tony knew from last time that he’d be hoarse by the time Loki was finished fucking him.

His ass clenched and his mouth fell open when Loki thrust up against him. Tony felt like he was being split open, stuffed full and thoroughly owned all at once with how completely Loki seemed to surround him. It burned, it _hurt_ , but that didn’t stop him from wanting every inch of Loki to be buried inside of him. Behind him, braced and releasing sounds of pure enjoyment, Tony could hear Loki speaking in another language.

By the tone it was more than obvious how pleased Loki was with him.

“ _Fuck_.” Tony’s fingers scrabbled at the rock he was spread out on, naked and aching, as Loki fucked forward again and again until he was completely buried inside. “Fuck. Somehow I forgot how fucking _huge_ you are.”

It was only the second time that he’d let Loki breach him, that he had let the creature from fairytales and myths, sheath himself inside and _fuck_ until Tony was a boneless mess.

“You’re the one with the small opening.” Loki tsked at him with amusement, “But it feels _so good_.” His voice was thick and filled with pleasure. Tony knew if he looked back Loki’s cheeks would be flushed and his eyes hooded, “My kind are not near as tight and warm inside.”

Tony’s mouth fell open on a wordless cry when Loki, still braced and in position, edged out and slammed back in with a near feral snarl that didn’t have a hope of covering up Tony’s shout.

His body trembled, his hole clenched and Tony whimpered at the steadily increasing pace as Loki greedily fucked his ass in an almost mindless way. Being so completely at Loki’s mercy, at a creature’s mercy, had lust and arousal singing through him in warm waves. He knew, from months of coming down to the rocks, that Loki was driven far more by instinct then rational thought.

That Loki lost himself to the pleasure of fucking wasn’t a surprise but it had been a surprise at how much Tony enjoyed the animalistic quality of it.

“Ohhhh please Loki oh oh oh ohhhhh.” His throat worked and his eyes stared unseeingly out at the ocean and the shoreline. It was luck that no one came this far out especially as the sun started to disappear from the sky. It had been drunk luck that Tony had stumbled across Loki in the first place.

A tentative, mutually curious relationship between the two of them twisting and twining until Tony had let Loki push into him. Now, only the second time, he knew he’d come back for more. The call, something that seemed to have hooked itself inside of him, was something he couldn’t resist and didn’t want to.

When Loki finished his ass would be absolutely wrecked, his muscles would protest pretty much any kind of movement but Tony would still wear the smile of a fucked out and completely sated twenty year old. A foolish boy if you asked the Board at SI but Tony didn’t give a fuck. Howard’s words, when he’d been alive, had done little to curb him and a bunch of greedy assholes didn’t matter.

“My name sounds perfect when you moan it.” Loki’s voice was smug and pleased as his pace picked up. It seemed almost every other forward thrust had that thick, wide cock nailing Tony’s prostate and sent bursts of pleasure racing through him.

Tony moaned and moaned, cheeks flushed from the lingering sun and his building pleasure, while Loki kept working himself forward. He could hear the hitches and the catches in Loki’s own breathing. Tony could almost sense how close the merman was getting to his release and it had him trying to shove back, to take Loki deeper yet, as he clenched and moaned brokenly.

He’d be walking with a limp for a few days but it was worth it. How could something that felt so good not be?

“Yesssss.” The word was hissed and Loki’s pace had turned brutal. He was slamming forward. Tony could only lie there, mouth moving soundlessly save for a few times wrecked whines managed to make themselves heard, as pleasure burst through him repeatedly.

It didn’t seem fair that he would never find a human so well-endowed or who wouldn’t care that he was Tony Stark. Loki didn’t care. The only things he knew of Tony were those they had talked about and what he’d managed to deduce. He also knew how Tony sounded when he was getting fucked and how loud Tony moaned when he came.

To Loki he was a pretty, brown-eyed little human that made beautiful sounds when stuffed completely full and caught on the end of Loki’s cock.

At least that’s what the merman told him.

Tony panted and shuddered as he managed to reach under himself to start stroking his achingly hard cock. It had his hips jerking and stuttering as he chased his pleasure. His hand moving had his ass clenching at the stimulation and his toes curling in pleasure as he stroked himself to orgasm.

The crash of the waves and Loki’s own sounds of delight worked together to drown out the loud, wrecked moan that ripped itself from his throat.

As he shuddered through the warmth of orgasm while his heart raced Tony went completely limp as he panted against the wet rock under him. Now each drag of Loki’s thick cock through his stretched hole had whines of too much tearing themselves from him.

“Oh fuck.” His fingers scrabbled at the rock and Loki slammed deep, groaning against him, and Tony could _feel_ Loki’s thick, warm release pumping into him. It was far more than any human could produce, another sign of their more than obvious differences, and left him feeling heavy.

The feeling of being completely owned was heady and Tony basked in the sensation.

Soft lips brushed against his shoulder blade and Tony felt himself being guided off the rock, into strong and able arms, as Loki practically nuzzled against him and half of his body disappeared under the waves. Sounds indicating Loki’s pleasure and affection for Tony brushed against his hair.

All the while Loki remained firmly buried inside of Tony.

“If only.” The words were almost whimsical, practically sighed against him, as a long fingered hand idly stroked against his flat stomach where, if he looked down, Tony knew he’d be able to see the outline of Loki’s cock. “It’s in my power but would you? Would you allow it?” Loki’s voice had lowered as though Tony wasn’t supposed to hear the wonderings the merman was giving voice to.

Tony sighed at the soft touches and the affection that swelled inside of him. It was nice to have someone touching him so softly and carefully, as though he were infinitely precious for himself instead of his name. Tony relished Loki’s hands touching him as though he was _loved_ and _treasured_.

“Keep that up and I might think you’re getting attached.” He mumbled, not fighting the touches or hold and instead sinking into it. _Touch starved_ his mind lazily offered up from a pointless Psychology course he’d taken. “Thought a fierce merman like you wouldn’t do that.”

“It’s… _nice_ to have something of my own.” Lips brushed him again, almost claiming and possessive, as Loki’s hand continued to idly stroke him.

Tony blinked at the rocks in front of him and the beautiful blue of the ocean.

“Will you come back?”

Loki always asked it as though he believed Tony would abandon him, as though he was used to being chosen last, and Tony nodded. At this point he would be lying to himself if he said Loki was the only one getting attached.

 _Fuck_.

**Author's Note:**

> This bingo square has been kicking my ass for what feels like forever. I'm not 100% happy with it, if I'm completely honest, but I feel like I managed to get it to a place that was at least interesting. Also, yes, Loki was thinking about using his magic to turn Tony into a merman like him.
> 
> I've seen a few merman/human pieces of fanart with smut and I borrowed from those to figure out the best way for merman/human sex. Also who doesn't love size kink? This seemed like the perfect opportunity for it.
> 
> So...let me know what you thought about this one! I hope, as I always do, that a few of you enjoyed it.


End file.
